Method and device for pumping a gas



' SR sa a Room Hpgggg XR 3924147490 M038 REFERENCE March 22, '1966 P.RlCATEAU ETAL METHOD AND DEVICE FOR PUMPING A GAS 3 Sheets-Sheet 1 FiledJune 26, 1962 P. RICATEAU ETAL 3,

MEH'Y'IOID AND DEVICE FOR PUMPING A GAS March 22, 1966 Filed June 26,1962.

3 Sheets-Shoot 3 United Smtes Patent Ofice 3,241,490 Patented Mar. 22,1966 METHOD AND DEVICE FOR PUMPING A GAS Pierre Ricateau, Garches, andCamille Vavasseur, Clamart, France, assignors to Commissariat a lEnergieAtomique, Paris, France Filed June 26, 1962, Ser. No. 205,330 Claimspriority, application France,'.luly 3, 1961,

866,745, Patent 1,301,307

7 Claims. (Cl. 103-1) The'mo'unting or. fitting of this component whichis adapted to move inside the pump body or compressor body usuallyentails accurate tolerances while the movement thereof calls forappropriate mechanical qualities of the material employed.

Moreover, it .is known that in the case of corrosive gases or gaseshaving very high temperatures, it is extremely difficult or evenimpossible'to find a material which can be machined to the requisiteprecision while having sufficient mechanical strength andlength of lifewhichare compatible with effective utilization.

The present invention has .for its object both a method and device fordriving a gas which eliminates all mov- .ing parts and dispenses withthe need for strictly accurate tolerances when machining other parts ofthe apparatus.

This method of pumping a gas through a propulsion zone in a givendirection makes use of the combined action of a permanent magnetic fieldand a permanent electric field, the directions of which are at rightangles to each, other and at right angles to the direction ofpropulsion, and mainly consists in effecting the ionization of .the gasat the input end of the propulsion zone at a repetition rate such thatthere exists at each moment an electric are which is orientated in thedirection of the electric field and which is movable 'in the directionof propulsion.

The device which serves for the practical application of the abovemethod is characterized in that it comprises in combination means forconfining the zone of propulsion of the gas to be pumped and forproducing in the said 'zone a magnetic field at right angles to thedirection of propulsion, means for maintaining between two mainelectrodes or sets of electrodes extending in the direction ofpropulsion a continuous potential difference producing an electric heldat right angles to the magnetic'ficld direction and to the direction ofpropulsion, and means for striking an are through the gas to be drivenat the input end of the said propulsion zone and at a pre-determinedrepetition rate,

Further characteristic features of the invention wil be more clearly andprecisely explained in the following description of various examples ofembodiment which are given by way of indication without any limitationbeing implied.

In the accompanying drawings:

FIG. 1 illustrates the method of propulsion employed.

FIGS. 2, 3, 4 and illustrate various means for ionizing the gases to bedriven.

FIG. 6 shows in cross-section at right angles to the direction ofpropulsion, the complete pump assembly in accordance with the presentinvention and making use of the ionization means of FIG. 2.

Only those elements have been made to appear in the figures which areessential to the understanding of the invention, while correspondingelements shown in these figures have been given identical referencenumbers.

The principle of propulsion is illustrated in the exploded view ofFIG. 1. The gas arrives through the inlet pipe 1 and passes out throughthe outlet pipe 2. One or the other of these pipes can be simpleopenings when suction or delivery takes place in free air. Between thesetwo pipes is located the pumping passage 5 which is closed both at thetop and bottom by electrically insulating walls which are preferablyconstituted by plates of refractory material, the said pumping passagebeing closed on its two other faces by electrodes 6 and 7 between whichan arc is to be established. The said electrodes can be either cooled ornot \by internal circulation of a cooling liquid such as water, and canbe constructed of a material which is customarily employed in thetechnique of electric-arc formation and which is suitable for use atvery high temperatures, such as graphite. Such electrodes can also bemade of metal, on condition that the surface of this metal is maintainedby appropriate cooling means at a temperature which is compatible withits length of life.

In the pumping passage is located an upwardly directed magnetic fieldwhich is produced by a permanent magnet or an electromagnet, the northand south poles of which are designated by the references 3 and 4respectively.

The electrodes 6 and 7 are supplied with direct current from a sourcewhich is designed to provide sufficiently high voltage and currentintensity to maintain an are previously struck between the electrodes inthe presence of the magnetic field and in spite of the dynamic effect ofthe flowing gas; Although it is not essential to do so, it is possibleto improve the stability of the are by means of an inductance coilconnected in series in the supply circuit or by means of ahigh-frequency source which delivers current between the same electrodes6 and 7 or by means of these two arrangements at the same time.

It is known that unless there is a very high voltage between theelectrodes 6 and 7, the arc does not strike spontaneously. Even if aspecial arrangement such asa spark initiates the :arc in region 8,experience has shown that the are, which is blown as a result of theaction of the magnetic field, is displaced towards the outlet 2 of thepassage and is then broken.

If it is desired to prevent the interruption of the current between 6and 7, the arc must be restablished in region 8 at the very moment whenthe breaking of the previous arc takes place at the outlet of thepassage.

To this end, a permanent plasma is formed in accordance with the presentinvention, in region 8 of FIG. 1. The

function of the said plasma is to initiate the arc in region 8.

and to compel the arc to re-form in this region each time it isinterrupted.

The pemianent plasma can be produced by a second direct-current arewhich is initiated in region 8 parallel to the lines of force betweenthe auxiliary electrodes 10 and 11, this arrangement being showndiagrammatically in FIG. 2. As in the case of the main arc, theseelectrodes can be cooled by the internal circulation of a cooling fluid.The permanent plasma can also originate from a highfrequency dischargewhich can be initiated either between the electrodes similar to 10 and11 or between an electrode 12 and the electrodes 6 and 7 of the main areas indicated in FIG. 3. In the case of a high-frequency discharge, thesaid discharge can follow a direction which is different from that ofthe lines of force. The said permanent plasma can also be produced bymeans of a highfrequency dis- 3 charge which is induced inside acoil-winding without being brought into direct contact with the plasma(as shown in FIG. 4). In this latter case, the discharge thus induceddoes not usually take place spontaneously and must be established byanother means at .the time of setting the apparatus to work.

The above-mentioned devices for re-forming the are have the disadvantageof creating a very hot zone which is localized at the inlet of thepassage and which is consequently subject to increased erosion.

One improvement consists in striking the are by producing a moving arehaving a frequency of movement which is either very high or equal to awhole multiple of the repetition frequency of the main arc.

The principle of this new arc-striking device is illustrated in FIG. 5.A new electrode 9 which can be of the same material as the electrodes 6and 7 has been housed and 9 brings the electrode 9 to a positivepotential with respect to the electrode 6. This auxiliary source canhave a lower power output than that which produces the main arc.

In view of the polarities adopted, when an auxiliary arc is struckbetween the electrodes 9 and 6, the said arc, being subjected to thefield of magnetic force, is caused to move around the electrode 9. Eachtime that the arc travels into the region 8, it introduces a burst ofplasma into the pumping passage, thus having the effect of strikingthe'main arc. It is possible, for instance, by means of magnetic devicessuch as auxiliary magnetic cores modifying the magnetic circuit of theelectromagnetic field to regulate the field of force in the zone of theauxiliary electrode in such manner that the auxiliary arc isFE-BSlIablished at the point 8 at the precise moment when the main arcis suppressed at the outlet 2 of the pumping passage. By providing asufiicient frequency of the auxiliary are, it can also be made possiblefor this latter to appear in region 8 at'least once during the period ofbreaking of the main are at the outlet of the driving passage. In thislatter case, the said frequency does not need to be regulated withprecision.

v The apparatus operates as follows: when the plasma appears in region8, an arc is formed between the main electrodes6 and 7. If I designatesthe arc current, B the magnetic induction, L the distance between mainelectrodes, a force F=IBL appears, is applied to the gas and initiatesthe-propulsion thereof. When the current I is sufiicient, the arctravels from the-passage inlet towards the outlet and is broken at theoutlet; another are is then formed again in region 8 by virtue of thepresence in this region of a strong continuous ionization, this new aretravels in turn in the same manner and so forth. In view of the rapiddisplacement of the are, there is distinctly less heating and wear ofthe electrodes 6 and 7 than in the case of a stationary arc, the currentintensity being equal.

It will be observed that in one case as in the other, although theconductive zone represents'only a part of the zone which is subjected tothe field of magnetic force, the so-called Rayleigh-Taylor" instabilitywhich could have a detrimental effect on the operation does not in facthinder the propulsion of gas.

It has been stated above that, as a result of the absence of movingparts, of accurately machined components and parts requiringspecialmechanical strength, this method of propulsion was particularlywell suited to the propulsion of corrosive or very hot gases. Aparticularly important application is that of high-temperature windtunnels. Accordingly, by virtue of this method, the hot gas can beretained in the return circuit instead of being discharged into theouter air. The result thereby achievedis a'con'sidorable saving ofpower.

An application of a different nature is that of the propulsion of gasesat pressures which are lower than atmospheric pressure. In this newapplication, the method offers the advantages of absence of sealingjoints as employed in mechanical transmission systems and absence ofvapours of foreign gases such as vapours from lubricating oils ofmechanical pumps or mercury vapours of molecular pumps.

The complete gas pump assembly in accordance with the present inventionis illustrated in FIG. 6 (seen from the input end of the passage). Theapparatus is designed to entrain air at atmospheric pressure.

The device is placed between the poles 3 and 4 of a direct curentelectromagnet, the magnetizing coils of which are designated by thereferences 13 and 14, and which is capable of producing a magnetic fieldof 2,000 Gs in the pumping zone. The passage 5 of square section, withsides which each measure 6 mm., is closed both at the top and bottom byisolating refractory plates 15 and 16 and laterally by main electrodes 6and 7 of graphite. The said main electrodes are connected through aninductance coil which has not been shown in the drawings to a directcurrent drooping-characteristic generator, the excitation of which isregulated in such manner as to obtain, for example, an arc of 150 amp.at 45 v. between the said electrodes. The auxiliary arc jumps betweenthe electrodes 11 and 10.which are placed at the entrance of the passageinside an enlarged portion of the main electrodes; the said auxiliaryarc is fed from an independent current source which can be adjusted to40 amp. at 40 v.

As soon as the auxiliary arc is struck, the main arc is struck in turnand then displaced. At the same time, the air is set in motion insidethe passage.

What is claimed is:

1. In a method of pumping gases through a propulsion zone in a givendirection by means of the combined action of a permanent magnetic fieldand a permanent electric field the directions of which are at rightangles to each other and at right angles to the direction of propulsionof the gas, the step of ionizing a portion of the gas adjacent the inputend of the propulsion zone at a repetition rate such that electric arcsare created approximately at the time the preceding arc leaves thepropulsion zone and which are oriented in the direction of the electricfield and then moving the electric arcs in the direction of propulsionof the gas by the action of said fields.

2. A device for pumping gas comprising means for confining a zone ofpropulsion for the gas to be pumped, means for producing in said zone amagnetic field at right angles to the direction of propulsion of thegas, main electrodes extending in the direction of propulsion of thegas, means for maintaining between said main electrodes a continuouspotential difference producing an electric field at right angles to thedirection of the magnetic field and to the direction of propulsion ofthe gas and means for striking arcs through the gas to be pumped at theinput end of the propulsion zone'and at a predetermined repetition ratesuch that arcs are created approximately at the time the preceding arcleaves the propulsion zone, said fields moving said arcs in thedirection of propulsion of the gas.

3. A device as described in claim 2 in which said arestriking meanscomprise two auxiliary electrodes connected across the terminals of asuitable electric current source, the common axis of said auxiliaryelectrodes being parallel to the magnetic field.

4. A device as described in claim 2 in which said arestriking meanscomprise at least one auxiliary electrode which is connected to ahigh-frequency electric current source with its circuit completedthrough one of said main electrodes.

5. A device as described in claim 2 in which said arcstriking meanscomprise a coil-winding which is connected to a high frequency electriccurrent source.

6. A device as described in claim 2 in which said arestriking meanscomprise at least two auxiliary electrodes, an electric non-alternatingcurrent source connected to said auxiliary electrodes which is capableof maintaining a moving discharge between said auxiliary electrodes andan annular discharge zone between said auxiliary electrodes subjected tothe field of magnetic force and communicating with the propulsion zone,the long axis of said annular zone and said auxiliary electrodes beingdisposed in a plane at right angles to the magnetic field.

7. A device as described in claim 6 in which said main electrodescomprise certain of but not all of said auxiliary electrodes.

6 References Cited by the Examiner UNITED STATES PATENTS 1/1941 Prince315-111 5/1960 Me lhart 315-168 OTHER REFERENCES LAURENCE V. EFNER,Primary Examiner.

1. IN A METHOD OF PUMPING GASES THROUGH A PROPULSION ZONE IN A GIVENDIRECTION BY MEANS OF THE COMBINED ACTION OF A PARMANENT MAGNETIC FIELDAND A PERMANENT ELECTRIC FIELD THE DIRECTIONS OF WHICH ARE AT RIGHTANGLES TO EACH OTHER AND AT RIGHT ANGLES TO THE DIRECTION OF PROPULSIONOF THE GAS, THE STEP OF IONIZING A PORTION OF THE GAS ADJACENT THE INPUTEND OF THE PROPULSION ZONE AT A REPETITION RATE SUCH THAT ELECTRIC ARCSARE CREATED APPROXIMATELY AT THE TIME THE PRECEDING ARC LEAVES THEPROPULSION ZONE AND WHICH ARE ORIENTED IN THE DIRECTION OF THE ELECTRICFIELD AND THEN MOVING THE ELECTRIC ARCS IN THE DIRECTION OF PROPULSIONOF THE GAS BY THE ACTION OF SAID FIELDS.